The invention relates to a fuel injection system for an internal combustion engine, with a high-pressure pump for pressurizing the fuel and at least one injection valve, with a supply line, which connects the high-pressure pump to the injection valve. The fuel supply line includes a multi-way spool valve with a valve housing in which a valve spool is movable by an actuator, such that a flow connection can be established from the high-pressure pump to the injection valve or from the injection valve to a return located at the low-pressure side of the fuel system and, furthermore, with a supply flow throttle in the flow connection.
DE 199 21 878 A1 discloses a fuel injection system for an internal combustion engine, in which a multi-way valve which is activated by a solenoid valve and which has a pressure control piston is arranged between a high-pressure accumulator and an injector. In this system, the injection pressure can be set in a controlled manner only within specific limits. Tolerances unavoidably occurring along the injection-pressure profile cannot be compensated by means of this system.
It is the object of the present invention to improve a fuel injection system of this type, to the effect that, in the event of tolerances occurring along the injection-pressure profile, these tolerances can be effectively counteracted by simple measures.
In a fuel injection system for an internal combustion engine with a high pressure pump for supplying pressurized fuel to fuel injection valves and a multi-way valve disposed in the high pressure fuel line to the fuel injector for controlling the fuel flow to the injector, the multi-way valve is a spool valve which includes an actuator for positioning the spool to provide selectively a flow connection between the high pressure pump and the injection valve or between the injection valve and a fuel return line and which further includes an inflow throttle structure forming a pressure control device. A pressure sensor is arranged between the spool valve and the fuel injector and supplies the sensed pressure value to a controller which compares the value with predetermined set values and provides a correction value to the multi-way valve actuator for the correction of the pressure of the fuel supplied to the fuel injection valve.
With the fuel injection system according to the invention, the injection pressure can be fully and accurately controlled. The influence of the component tolerances on the injection can be at least largely eliminated. Because the pressure is continuously monitored, malfunctions of the fuel injection system can also be detected at an early stage and possible damage can be avoided.
The system according to the invention can easily be used in existing fuel injection systems as a retrofit solution, specifically as a component in which the regulating valve, sensor technology, actuator and controller are integrated. Only the corresponding power supply and the connection to a central computer for transmitting the desired pressure values are required.
The fuel injection system according to the invention is described below on the basis of the accompanying drawings.